History of Aircraft Propeller

The concept that led to propeller propulsion was derived from the rotating screw design, invented by Archimedes in 200 BC. This design was used to lift water from wells and was an inspiration for Leonardo Da Vinci’s flying machine. Although his helicopter-like design was never built, it inspired many aviation innovators. By the mid-1700s, the rotating screw design was also used in marine propulsion.

It wasn’t until the early 1900s that propellers were effectively used for flight. The Wright brothers used their wind tunnel test to study the aerodynamics applied to propeller blades and realized that propellers should be shaped more like a wing than a screw, and that it’s more efficient to add a twist along the length of the propeller blade. Today, propellers come in a vast array of styles that vary in size, shape, material, and application.

Propellers transmit power by converting rotational motion into thrust. They are attached to shafts and receive their energy supply from different types of engines. Once the propeller is spinning, it begins producing forward thrust. This can be explained through Bernoulli’s principle and Newton’s third law of motion. Bernoulli’s principle states that an increase in a fluid’s speed occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy. Newton’s third law of motion states that when body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude but opposite in direction of the first body.

Propellers have angled blades because it increases its speed capabilities and requires less force. Propeller blades are twisted because different parts of a propeller move at different speeds. To ensure that they produce a constant thrust at each point, the angle of attack needs to be different along the blade. The pitch, or angle of attack, varies under different scenarios.

Some aircraft— mainly lighter ones— have fixed pitch propellers: the blades are permanently fixed to the hub. Larger and more advanced aircraft have variable pitch propellers which include adjustable pitch propellers, controllable pitch propellers, and constant speed propellers. Adjustable pitch propellers allow the operator to adjust the pitch while grounded. Controllable pitch propellers allow the operator to adjust pitch during flight. Constant speed propellers automatically adjust pitch during flight. One of the benefits of having variable pitch propellers is that they have the ability to feather if an engine fails. This means that the blades are turned edge on, making a shallow angle to oncoming air, which minimizes drag and allows an aircraft to fly on the other engines or glide.

At NSN Purchasing, owned and operated by ASAP Semiconductor, we can help you find all the aircraft propeller parts you need, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we’re always available and ready to help you find all the parts and equipment you need, 24/7x365. For a quick and competitive quote, email us at sales@nsnpurchasing.com or call us at +44-142-035-8043.


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Importance of Rotorcraft Blades

One of the most important parts of any rotorcraft is undoubtedly the rotor. But the blades are a close second. Afterall, for rotorcraft, the rotational movement of the blades is the only reason that the aircraft can even achieve lift and fly.

For rotorcraft like helicopters, lift is achieved when the rotor blades (airfoil) meet the oncoming airflow and deflect them, creating a change in the direction of the airflow, which results in an area of low pressure forming behind the leading edge of the upper surface of the blade. In turn, this pressure gradient causes the air flow to accelerate down along the upper surface. Simultaneously, the airflow under the blade is rapidly slowed or halted, causing an area of high pressure, also causing the airflow to accelerate along the upper surface. The two sections of the airflow leave the trailing edge of the blade with a downward component of moment, producing lift. In order to withstand the airflow and effectively be lifted, the blade must be strong and durable enough. Therefore, it’s important to test the blade flex.

Rotor blades are dynamic devices, so of course it’s important to regularly inspect and test their functionality. However, equally important is a static test to verify the strength and mechanical properties of the blades. Because the environmental conditions and operating conditions of the blades can vary greatly, it’s good to make sure, during the manufacturing process, that everything is up to standard.

The static test is done by mounting the rotor blade horizontally on a stationary fixture at one end, a hydraulic ram at the other with LVDT (linear variable differential transformers) displacement sensors arranged along the length of the blade, and a strain gage load cell inserted between the hydraulic ram and blade tip. Pressure is applied to the ram, flexing the blade. Meanwhile, the load cell senses the amount of force while the LVDTs measure the amount of bending. These two readings are calculated as a ratio of force to bending and help determine the strength and flexibility of the blade. The ideal ratio is typically set by the OEM (original equipment manufacturer).


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Aircraft Propeller

The propeller is the one of the most vital parts on your aircraft, and one of the most vulnerable. The aircraft propeller is the main component used to generate thrust, consistently stressing the propeller. The likelihood of the propeller sustaining damage is substantially higher than it is for the rest of the airframe. So, it’s important to care for the propeller and conduct regular visual inspections. Fortunately, proper propeller care doesn’t require a specialized technician, nor will it take a lot of time. By following these few easy steps, you can remain vigilant on your propeller’s condition and remain confident when cruising at 15,000 feet.

The first place to begin is the preflight visual inspection. Make it a habit to regularly take an extra minute or two to inspect the propeller. When conducting the visual inspection make sure to keep an eye out for any visual damage on the aircraft propeller blades. You should be on the lookout for any signs of cracks, chips, dents, gouges, and erosion. To be completely thorough, make sure there’s no missing hardware. It’s a good idea to lightly drag your hand across the propeller to help you detect any abnormalities. If there are any discrepancies, delay your flight and address the issue.

As you may know, the aircraft should only be moved utilizing proper ground support equipment, such as a tow bar, to safely move the aircraft. This is the easiest precautionary action you could take to avoid unnecessary damage to your aircraft. Cutting corners may save time, but you’re much better off following the correct procedures from beginning to end. Pushing and pulling on the prop is a perfect recipe for a trip to the repair station.

Lastly, stay on top of maintenance and overhaul schedules. Maintenance intervals can be based on calendar time or flight hours, so be sure to keep track. Following the manufacturer’s recommendations will help prevent any major accidents from occurring.

Be sure to keep NSN Purchasing, owned and operated by ASAP Semiconductor, at the top of your list for any part requirements. NSN Purchasing is the premier supplier of aviation components. New or obsolete, we can help you find all the parts you need, 24/7x365. For a quote, email us at sales@nsnpurchasing.com.


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